First install server and then try browser with ip and port.
if the installation correct then browser will show login page.
once installation over then check the port you added in configuration window. and also check the tableau server is running or not.
Try using the URL localhost/ (with the slash) instead of www.localhost.com from a browser in the primary server. You shouldn't have to specify port 8000 unless you deliberately changed the default port to it.
If you are connecting from anywhere other than the primary server, use the static IP or DNS name assigned.
Is this an upgrade installation (from a prior version to a newer version)? What version are you trying to install? Is it a single server or do you have workers as well, and if so, how many?
ditto to what Toby asked. I'm running into my own issue upon trying to run a restore of data after an upgrade to 9.0.4 and I have opened a case with support.
Please provide a bit more details.
www.localhost/ is never going to work....but the fact that the server page isn't coming up after a new install doesn't sound healthy.
On the Primary try checking server status via Tabadmin or http://localhost/admin/systeminfo on the gateway machine.
You can also usually see what went wrong in the tabadmin.log file as well, but it keeps happening I'd raise with Support....